There are many parts of a computer, but I’ll list out the main parts that are commonly used in order to build a computer:

1) Processor (Or CPU [Central Processing Unit]): I consider this the brain of the computer. This processes (hence the name) most of the tasks you want a computer to do, such as opening programs, playing videos, doing calculations, etc. This is where all information gets passed through and for you to use the computer.
Motherboard: This is where all the components of a computer gets connected. There’s a lot of connectors and other electronic components here to make the computer function.
2) RAM (Random Access Memory): This is where temporary but fast storage is located. The computer decides what programs it wants to load very quickly and places them here. Once it is done, the computer will save all that information into the hard drive for long term storage. Once you turn off your computer, the information in RAM disappears. The more programs you use at once (multiple tabs on a web browser, many programs runing at once), the more RAM you’ll need to hold all this information.
3) GPU (Graphics Processing Unit): This is like the CPU, but it is focused on graphics. It will process the graphics for information to be converted into pictures you are able to see on the monitor. Many computers have this integrated with the CPU (AMD calls this an APU [accelerated processing unit]).
4) Hard Drive (HDD [Hard Disk Drive], SSD, NVME, etc.): As stated in the RAM section, the hard drive holds long term information. This is where your computer can access the saved programs and documents even when the computer was turned off.
5) Power Supply: This is what provides the electricity for the computer to run.